Animal Locomotion

Abstract

THERE are two or three points in Dr. Pettigrew's new book as to which, perhaps, many of your readers in common with myself would be glad of a little light First, in speaking of the gannet, he says: “Each wing, when carefully measured and squared, gave an area of 191/2 square inches.” But how is such an area obtained from the dimensions given? They are: “girth of trunk, 18 inches,” i.e., about 5 inches for its width; “expanse of wing from tip to tip across the body, 5 feet,” so that each wing would stretch about 331/2 inches from root to tip; “across secondaries, 7 inches,” and this we may take as about the average width of the wing. Multiplying length of wing by width (331/2 × 7), we get therefore an area of 2341/2 square inches. Similarly Dr. Pettigrew assigns the heron's wing an area of 26 square inches, although the dimensions he gives yield an area of about 311 square inches. A friend of mine has the temerity to suggest That for some reason or unreason Dr. Pettigrew has divided the true area by 12, for so 2341/2 (if we neglect the half inch) gives just 191/2 and 312 instead of 311 gives 26.